1. Field of the Invention
The present invention relates to a bandsaw machine provided with an endless bandsaw blade, and, in particular, to a device for measuring the cross sectional shape and dimensions of a workpiece being cut in the bandsaw machine, and a device for automatically adjusting the position of a saw blade guide which guides the saw blade to conform to the shape and dimensions of the workpiece.
2. Description of the Prior Art
When a material is being cut by a bandsaw blade, it is desirable to uniformly control the cutting rate (surface area cut per unit time) or to know in advance the shape and dimensions of the workpiece in order to adjust the position of a saw blade guide which guides the sawblade on both sides of the workpiece.
Conventionally, the operator generally uses a scale to measure the shape and dimensions of the workpiece. Devices have been proposed to make such measurements automatically, such as the device with the configuration outlined in U.S. Pat. No. 4,432,260. In the abovementioned prior art, when the workpiece is secured in a vise device the width of the workpiece is measured using a scale means connected to the vise device, and the height of the workpiece is measured using a scale means in the vertical direction.
Accordingly, it is possible to measure the width and the height of the workpiece automatically. However, there is no facility for judging if the shape is square or circular, and therefore the judgment of the shape of the workpiece is dependent on the observations of the operator.
In recent years, the need has arisen for a device to automatically convey a workpiece into the sawing machine to allow the cutting of many different types of workpieces automatically. This requires automatic measurement of the shape and dimensions of the workpiece in the sawing machine.
In addition, it is desirable to be able to reduce the distortion and the vibration of the band saw blade of a band saw machine when it is cutting into the workpiece.
Regardless of the type--horizontal or vertical--for a band saw machine it is normal to provide a saw blade guide for guiding the saw blade on each side of the workpiece. Conventionally, one of these saw blade guides is set in a fixed position while the other is usually adjusted beforehand to a position conforming to the maximum length of cut in the workpiece. Accordingly, when, for example, the workpiece is a round rod, the spacing of the saw blade guide is set large enough to conform to the diameter of the round rod. For this reason, when the saw blade first contacts and begins to cut into the round rod, the length of cut in the round rod is extremely short with respect to the dimensions of the spacing of the blade guides on each side of the saw blade. Therefore, not only is the band saw blade easily twisted and bent, but severe vibration of the saw blade can also be produced.
Specifically, in a conventional band saw machine the adjustment of the position of the saw blade guides must be performed manually. The problem therefore arises that, not only is the adjustment of the blade guide position a great deal of trouble, but bending of the saw blade readily occurs at the first cut.
In consideration of the problems associated with such conventional devices, technology has been developed to automatically adjust the spacing of the saw blade guides to conform to changes in the length of the cut in the workpiece. Specifically, such technology is disclosed, for example, in U.S. Pat. No. 4,363,254. This prior art incorporates a configuration in which one of the saw blade guides is moved by means of a hydraulic cylinder which is controlled by a changeover valve, and the changeover valve is controlled by means of a profiling contact member which is moved by the workpiece.
Accordingly, in this prior art, as the saw blade advances to cut into the workpiece, the contact member must smoothly profile the workpiece, and this requirement limits the shape of the workpiece. Specifically, cutting a workpiece with a complicated shape, for example, shape steel or a plurality of rod-shaped workpieces in bundles, is difficult to implement.